An insurance agent named Joe Rogers (Steve Forrest) is told by his boss, Sam Henderson, (Philip Coolidge) that he had been going through old files and had found a life insurance policy taken out by Marguerite Gillespie (Gladys Cooper). He is suspicious because her husband had died six weeks after she took out the policy. His boss is ticked off that Joe gave her $50,000 without checking anything. Joe says she was overseas at the time and her lawyer took care of it. He hadn't seen anything suspicious. His boss says he looked for and found another policy for Mrs. Gillespie, with a letter in the same handwriting, insuring her first husband for the same amount. This one, too, had died right after the wedding. He tells Joe there must be something funny going on.
Joe and his wife (Kathleen Maguire) go to the town where she lives to find out whatever he can.
At the hotel, he gets suspicious about a mystery man (Ned Wever) who seems to be watching them. The man goes out to the lobby, and Joe follows. He manages to overhear the desk clerk (Mason Curry) answering a question about how long Mrs. Gillespie has been living in town. He decides it must be an investigator from the same insurance company, checking up on him. Joe assumes the company doesn't trust him to be thorough.
Joe and his wife meet with the local realtor, Mr. Graham (Hal K. Dawson), pretending they're interested in buying a house. She mentions the address of Mrs. Gillespie, and the realtor says it's definitely not for sale, but she enjoys showing the house to visitors. Joe goes over there alone. The door is opened by a maid (Hope Summers), and she pleasantly invites him in. Mrs. Gillespie offers him tea and is very charming. She almost has him suckered, but during his visit, who should walk in but her future third husband, Howard Fieldstone. They're going to sell the house and go on a honeymoon. But it's a secret.
Well, he leaves, knowing full well she's guilty of two past murders, but not knowing how to prove it. On leaving the house, he runs into the other agent waiting on the front porch. "Any luck?" he asks. Joe says "I don't know what you mean", and stalks off. That night, a telegram is delivered by a bellhop (Mickey Kuhn). Joe's company has finally discovered that Mrs. Gillespie took out a policy on her soon-to-be husband through another branch of the company.
The next day at their hotel, he's sitting with his wife when she sees the investigator coming back in and points him out as the man who was watching them. Joe doesn't say he ran into him. Minutes later, Howard Fieldstone comes in. He sits with them for a few minutes, and Joe mentions Mrs. Gillespie had lost a husband. Fieldstone says Joe's mistaken, that she's been a widow twice. But he hopes she has better luck with the third. Joe comments that Fieldstone looks the picture of health and bets he could even pass an insurance physical. Fieldstone says he has no use for insurance, but as a matter of fact, Mrs. Gillespie had wanted him to get a physical, and he said he wouldn't do it unless she had one too, so they both had had one that very morning.
That night, in their room, he gets a call from the realtor reporting that the house has been sold, even though the couple had told him not to say anything. Joe rushes over to confront her, because he didn't "want that little old man to walk into a death trap." He arrives to find no one there but the realtor. He tells Joe that they're already gone to get married and go on their honeymoon. And they hadn't told anyone where they intended to go.
The other man who had been following Joe around barges in next, demanding to know where Mrs. Gillespie is. Joe tells him they're both gone. The man says "Now that it won't do any good, maybe you'll talk to me." He hands Joe his business card and introduces himself as Saunders. Yes, he's an insurance investigator, all right, but from a completely different company. Joe asks why the other company would be interested in Mrs. Gillespie, his target. Saunders reveals he's been checking up on Fieldstone.
Apparently he has had FOUR wives, all of whom died in the bathtub on the honeymoon. Joe tells Saunders his target has had two husbands die and get cremated before anyone could find out how they were poisoned. Saunders comments, "Well, they sort of deserve each other, don't they?" and says since they kept their destination a secret, there's nothing either of them can do. They sit, defeated, and Joe says, "Well, I suppose it all depends now on whether she takes her bath before he eats breakfast." Saunders says "Or vice versa."